USA Trends and Developments Contributed by: Matthew D Powers, Samantha Jameson, Azra Hadzimehmedovic and Aaron Nathan, Tensegrity Law Group LLP
written description in granting a preliminary injunc ‑ tion. Regeneron Pharms., Inc. v Mylan Pharms. Inc. , 127 F.4th 896 (Fed. Cir. 2025). The patent contained a description of the compound with its modifications and provided examples of stability measurements. Id. at 915. The defendant argued that the modified com ‑ pound had not been disclosed as having the required stability, but the patent owner’s expert successfully explained that one of ordinary skill would have read the stability examples as related to the modified com ‑ pound, and the defendant identified no rebuttal evi ‑ dence on appeal. Id. There were also disputes about the claimed stability range of “at least 98%” of the molecule in native conformation after two months. Id. at 915-16. First, the highest stability disclosed in the specification was just over 99%, not 100%. Id. Again, the expert testimony explained that “most proteins are not purified to 100%” and the upper bound of this range was “limited by what a relevant artisan would understand to be workable.” Id. at 916 (internal quo ‑ tation marks omitted). The defendant again did not show that stability over the disclosed range was “both possible and so difficult” as to make the range above that disclosed a “significantly different invention[].” Id. at 916. Second, the lower bound of this stability range was also sufficiently described because there were “multiple disclosures of native conformations through ‑ out the range of 98% to 100%.” Id. at 917. The lack of written description found in the CRISPR interference was influenced by another important factual determination: whether the technology is complex and unpredictable. This determination is particularly important because, “[w]hen the technol ‑ ogy at issue is ‘complex’ and ‘highly unpredictable,’” as was “uncontested” in the CRISPR case, “the level of detail required to satisfy the written description requirement may be greater.” Regents of the Univ. of Cal. v Broad. Inst., Inc ., 136 F.4th 1367, 1383 (Fed. Cir. 2025). Because “a person of ordinary skill in the art would have been aware of the complexities and the unpredictable nature of adapting prokaryotic sys ‑ tems to eukaryotic cells,” two provisional applications that “failed to disclose specific instructions or condi ‑ tions necessary” for activity in eukaryotic cells “or an indication that no specific instructions or conditions were necessary” did not “establish possession” of the CRISPR invention in eukaryotic cells. Id.
Xencor is an important reminder that broad claims require sufficiently broad descriptions, and the claims in Xencor were found to lack a sufficient written description in light of their scope. First, preamble lan ‑ guage “treating a patient” was found to be both limit ‑ ing and lacking an adequate written description. In re Xencor, Inc. , 130 F.4th 1350, 1359 (Fed. Cir. 2025). The specification did “not include any example of treating a disease or condition” with the claimed antibody, let alone treating “all diseases” as contemplated by the claim. Id. at 1359-60. Second, Xencor addressed the written description requirement for Jepson claims that are expressly directed to an improvement to the prior art. Id. at 1361. Because the invention in a Jepson claim “is not only the claimed improvement,” but the “claimed improvement as applied to the prior art,” the written description requirement necessitates showing “that what is claimed to be well-known in the prior art is, in fact, well-known in the prior art.” Id. at 1361-62 (emphasis original). Because the claimed antibodies in Xencor had not been shown to be “well-known in the art,” the written description requirement was not met. Two other cases last year confirmed the importance of focusing on the scope of the claims themselves (and not infringement) when undertaking a writ ‑ ten description analysis. The Rex Medical decision affirmed a finding that a patent was not invalid for lack of written description for failing to describe the shuttle of the accused surgical stapler and explained the written description question is not “whether the specification provides an adequate description of the Accused Products, but whether the specification pro ‑ vides an adequate description of the claimed inven ‑ tion.” Rex Med., L.P. v Intuitive Surgical, Inc. , 156 F.4th 1289, 1306 (Fed. Cir. 2025) (internal quotation marks omitted). Novartis reversed a district court finding that claims lacked written description. Novartis Pharms. Corp. v Torrent Pharma Inc. ( In reEntresto (Sacubitril/ Valsartan )), 125 F.4th 1090 (Fed. Cir. 2025). Because the claim required two drugs to be administered “in combination,” the patentee did not need to describe later-discovered two-drug “complexes.” Id. at 1097- 98. While the accused product was a two-drug com ‑ plex, the defendant had stipulated to infringement and there was no “further issue regarding such complex ‑ es” on appeal. Id. at 1095.
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